19 U.S.C. § 1709

When used in this Act: (a) The term “United States”, when used in a geographical sense, includes all Territories and possessions of the United States, except the Virgin Islands, the Canal Zone, American Samoa, Wake Island, Midway Islands, Kingman Reef, Johnston Island, and the island of Guam. (b) The term “officer of the customs” means any officer of the Customs Service or any commissioned, warrant, or petty officer of the Coast Guard, or agent or other person authorized by law or by the Secretary of the Treasury, or appointed in writing by a collector, to perform the duties of an officer of the Customs Service. (c) The term “customs waters” means, in the case of a foreign vessel subject to a treaty or other arrangement between a foreign government and the United States enabling or permitting the authorities of the United States to board, examine, search, seize, or otherwise to enforce upon such vessel upon the high seas the laws of the United States, the waters within such distance of the coast of the United States as the said authorities are or may be so enabled or permitted by such treaty or arrangement and, in the case of every other vessel, the waters within four leagues of the coast of the United States. (d) The term “hovering vessel” means any vessel which is found or kept off the coast of the United States within or without the customs waters, if, from the history, conduct, character, or location of the vessel, it is reasonable to believe that such vessel is being used or may be used to introduce or promote or facilitate the introduction or attempted introduction of merchandise into the United States in violation of the laws respecting the revenue.